The field of the invention is furnaces particularly furnace structures having smoke and gas return.
The invention relates to a furnace structure for generating heat with more particular attention paid to improving efficiency of heat transfer without decreasing burning efficiency below that of prior art furnaces.
Overall improvement in efficiency is gained by:
(a) combining water and gas loops as completely as physical conditions can accommodate;
(b) increasing the dwell time of the two fluids with each other;
(c) expansion of the exhaust gases to ambient pressure or below to assist in a rapid heat transfer capability in the heat exchanger;
(d) operating the burner at high pressure and high gas density to achieve a high heat density;
(e) reduction of the mass flow rate of gas to atmosphere to the amount consumed in near stoichiometric burning conditions;
(f) reduction of the temperature of the discharge exhaust gases to the atmosphere well below the point where the chimney will function; and
(g) elimination of the chimney by providing a high pressure "blow-down" of exhaust gas to atmosphere to replace the chimney draft requirement.
None of the prior art furnace structures having smoke and gas return fulfill the above requirements.